BusinessDay contributing editor

Buy a small stake in a company, let it be known that you're a ginger group with some high-profile names, allow stories to circulate about a possible coup or maybe even that numbers are being sought for something bigger, become a factor in the share price rising – and then quietly sell out for a fat profit. Nice work if you can get it and that's what the Carnegie/Dixon/Singleton/Gregg boys got with their Qantas game.

Nothing illegal about that, of course. It is not insider trading. But, in my opinion, it's reasonable to wonder if it is something rather like insider trading.

Having the Carnegie gang on the books and known to be agitating for change at Qantas certainly did the Roo's share price no harm. It has outperformed the market since the ginger group surfaced in late November.

You might think that exiting that stake – with about an $18 million profit, according to the AFR - could cause the Qantas share price to fall. And it did. From the $1.515 close on Tuesday, Qantas shares dropped three per cent to a low of $1.465 this morning before partially recovering. At lunch time, it was still off 1 per cent in a higher market.

That's why you naturally wouldn't inform the market of any intention to sell before the action. You're not required to. You'd be silly to.

As the vendor though of such a high-profile "activist" stake, did the Carnegie crew have price-sensitive knowledge that the rest of the market did not? It's a reasonable question.

If you can build a reputation as a bit of a raider, just your name appearing on the register is enough to lift the share price and ensure a profit. Back in the wild old days of the '80s, Ron Brierley's Industrial Equity and similar souls did it regularly. Often enough, the emergence of a supposed raider's name could destabilise a company's register and trigger a bid from another party. Money for jam.

Of course, to maintain credibility, a raider needs to follow through occasionally. According to the AFR report, the 1.5 per cent Carnegie stake in Qantas was only held via certificates for difference – handy for a quick speculation, a little gamble, but an expensive way of holding stock for more than the short term. Maybe they were never really serious anyway.

The market might now wonder just how credible Carnegie and friends are the next time they pop up. Oh, that's right, they already have – as associates of Gina Rinehart on the Fairfax register.